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5.3 Internal Coolant Loss

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HELP!

I have a 1999 Silverado Z71 with a 5.3 that has slowly been losing coolant for about two years. I have had to add about one pint dexcool between regular oil changes.

Last month, at appx 75,000 miles, the low coolant light came on again and it was appx two quarts low this time after only going 500 miles from topping off coolant.

I am now seeing coolant inside the oil fill cap, not butterscotchy, but defenitely coolant.

I am suspecting intake or head gasket failure. Have there been problems with these or should I dig deeper. I added a small bottle of "BarsLeak" and this has temporarily solved the problem, but im not into rinky dink fixes. I am a mechanic by trade, but the 5.3 is a mystery to me, as I work on diesel rigs.

Any ideas to steer my in the right direction would be appreciated.

Or do I buy that new Toyota now?

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HELP!

I have a 1999 Silverado Z71 with a 5.3 that has slowly been losing coolant for about two years. I have had to add about one pint dexcool between regular oil changes.

Last month, at appx 75,000 miles, the low coolant light came on again and it was appx two quarts low this time after only going 500 miles from topping off coolant.

I am now seeing coolant inside the oil fill cap, not butterscotchy, but defenitely coolant.

I am suspecting intake or head gasket failure. Have there been problems with these or should I dig deeper. I added a small bottle of "BarsLeak" and this has temporarily solved the problem, but im not into rinky dink fixes. I am a mechanic by trade, but the 5.3 is a mystery to me, as I work on diesel rigs.

Any ideas to steer my in the right direction would be appreciated.

Or do I buy that new Toyota now?

 

 

It would be impossible for it to be intake related for the 5.3 is a dry intake. Why not pressure test the cooling system before jumping to conclusions? That's what I'd do, but hey you could always just go buy that perfect new Toyota. That way you can have the joy of owning Trannie problems, broken cams, frame flex (like the [email protected] things a slinky), and tin foil boddy pannels.

 

Just have the truck checked out.

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Are you absolutely sure you have coolant in the oil? If it is obvious then ok. If you have any doubt, do a quick oil analysis and that will tell you exactly how much coolant is in the oil, if any. The most common area of coolant loss on this engine is the water pump gasket. Especially on the earlier models. It typically will leak such a small amt that you will never see a drop hit the ground. Over time, it will get worse and worse.

 

I am not familiar with any head gasket issues with the 5.3 unless the truck has been hot. I am not a Prof Tech but in the Parts Industry and we see almost no internal issues with this engine.

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Good idea as suggested to check the Water Pump gasket. I had a leak and a mechanic told me it was the pump itself. It was a slow leak as you described. I bought a new pump, pulled the old, and noted that there was a leak in the right side gasket(drivers side). I replaced the pump anyway since I had it apart and I have 95,000 on my Avalanche.

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It could also be getting into the combustion chambers and burning off. My first thought would be head gasket.

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Are you absolutely sure you have coolant in the oil? If it is obvious then ok. If you have any doubt, do a quick oil analysis and that will tell you exactly how much coolant is in the oil, if any. The most common area of coolant loss on this engine is the water pump gasket. Especially on the earlier models. It typically will leak such a small amt that you will never see a drop hit the ground. Over time, it will get worse and worse.

 

I am not familiar with any head gasket issues with the 5.3 unless the truck has been hot. I am not a Prof Tech but in the Parts Industry and we see almost no internal issues with this engine.

 

Yep, I am 100% sure it is an internal leak as coolant droplets are forming inside the oil fill cap. I have been putting cardboard on the garage floor with no external coolant leaks visable.

The truck has never run hot or even had the temp flucuate. I can thank the "low coolant" light for that. This vehicle has been meticously maintained and never abused.

The coolant tank is staying full after installing the BarsLeak and no moisture is forming inside the oil cap anymore. I have changed the oil twice this month just to be sure no contamination exists. I sent the first oil sample to NC Machinery and am awaiting the results. I have been a professional mechanic since 1978 and have seen this condition many times before, especially with the 5.7 intake gasket problems. I have not had the oppurtunity to tear into a 5.3 yet as our fleet does not have any. I am just fishing for anyone who has experienced this problem before I rip the heads off.

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It could also be getting into the combustion chambers and burning off. My first thought would be head gasket.

My thoughts exactly. Before I installed the stop leak, I noticed some mornings when first started it would run a little rough for about 10 seconds, although no smoke was visable.

I may trade it in on something new this week. I was hoping to get 100k mi out of this rig before I traded it in. After all the problems i've had with this truck (nothing engine related), this will be the first time in 30 years a new Chevrolet has not been parked in my driveway.

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HELP!

I have a 1999 Silverado Z71 with a 5.3 that has slowly been losing coolant for about two years. I have had to add about one pint dexcool between regular oil changes.

Last month, at appx 75,000 miles, the low coolant light came on again and it was appx two quarts low this time after only going 500 miles from topping off coolant.

I am now seeing coolant inside the oil fill cap, not butterscotchy, but defenitely coolant.

I am suspecting intake or head gasket failure. Have there been problems with these or should I dig deeper. I added a small bottle of "BarsLeak" and this has temporarily solved the problem, but im not into rinky dink fixes. I am a mechanic by trade, but the 5.3 is a mystery to me, as I work on diesel rigs.

Any ideas to steer my in the right direction would be appreciated.

Or do I buy that new Toyota now?

 

 

It would be impossible for it to be intake related for the 5.3 is a dry intake. Why not pressure test the cooling system before jumping to conclusions? That's what I'd do, but hey you could always just go buy that perfect new Toyota. That way you can have the joy of owning Trannie problems, broken cams, frame flex (like the [email protected] things a slinky), and tin foil boddy pannels.

 

Just have the truck checked out.

 

 

Hey, I'm all for buying american. Thats why I have owned new Chevys for 30+ years.

I worked as a Toyota Master Mechanic for 10 years so I am familiar with their issues as well.

This truck (Made in Canada eh) has been a nightmare since day one and I refuse to take it to the dealer again since the extended warranty expired. Although I love the way it drives, it has had more problems than all the Chevy trucks i've ever owned combined. Nothing major, just transmission, transfer case, front diff, steering and brake issues all within the first 20k mi. (The truck is NEVER off road and all stock and driven by the wife)I have sent a oil sample in for analysis, but it's obvious there is coolant on the inside of the oil fill cap. Why pay the dealer to tell me i'm [email protected]#$%&, I already know that !

Just fishing here and looking for guidance before the wrenches fly. Thanks for the input.

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I had the same problem on my 01 GMC Sierra. I took it to the dealer at 37000 miles they ran a pressure check on it and replaced the water pump. In about a week i went back with the same thing, ran another pressure check and said all OK. It continued to leak and could not find any indication on the motor or under it. Right before my extended warranty ran out I took it back , same thing another water pump and still the problem.

At about 80000 miles the lifterswere replaced, they had been rattling for some time and had been back several times to the dealer, they finally could hear it real well this time. I didnt have that problem again untill just now, the coolant leak had gotten to where i had to add a quart every three or 4 days. Still no indication of where the leak was. As a last resort I added some Barrs to it and leak quit, but after a few days the lifters sounded like a thrashing machine. I guess the stuff had gotten into the engine. They ran some top end cleaner through it now and it runs fine. Actually like it did when new, as for now I dont have a coolant leak, but think this was problably the original problem with the lifters. Im hoping for the best but cant help but wonder what damage has been done with all of this.

 

Jerry

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Well if it isn't losing coolant after the barsleak, run it. I put that in my old '95 5.7 about 100K miles back. Had a crack in the water jacket on the outside of the block and it was dumping a cup overnight. Almost 350K on her now. It's been 5 years, but if it fails I guess it would still just have been a temporary fix.

 

However, if this truck has been a 9-year nightmare and you're looking for validation to buy a new truck . . . go for it. :D

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There is a new design head gasket (dual shim), its probably the head gaskets since there is very little other places it could come from

 

HELP!

I have a 1999 Silverado Z71 with a 5.3 that has slowly been losing coolant for about two years. I have had to add about one pint dexcool between regular oil changes.

Last month, at appx 75,000 miles, the low coolant light came on again and it was appx two quarts low this time after only going 500 miles from topping off coolant.

I am now seeing coolant inside the oil fill cap, not butterscotchy, but defenitely coolant.

I am suspecting intake or head gasket failure. Have there been problems with these or should I dig deeper. I added a small bottle of "BarsLeak" and this has temporarily solved the problem, but im not into rinky dink fixes. I am a mechanic by trade, but the 5.3 is a mystery to me, as I work on diesel rigs.

Any ideas to steer my in the right direction would be appreciated.

Or do I buy that new Toyota now?

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I came to this site looking for clues as to how others were dealing with dealers on the "Phantom Coolant Loss" issue, I was surpried that no reference was made to this in any greater depth. Here's what I know. I'm buying a 2004 GMC w/ 5.3 V8 from my employer. The truck has been losing small amounts of coolant over stretches of 400 to 600 miles. Come to find out long after the warranty was expeired of couse, there is a particular problem with one of the casting companies who made heads for this engine, castech is their name. At any rate here's the details from the tech bulliten I paid for, hopefully the pictures will show. It's a crying shame GM wont do anything given this is due to a defect in the casting of the heads.

 

 

 

Engine - Coolant Loss With No Visible Leaks

Bulletin No.: 06-06-01-019B

 

Date: June 12, 2007

 

INFORMATION

 

Subject:

Information on Gradual Coolant Loss Over Time With No Evidence of Leak Found

 

Models:

2004-2006 Buick Rainier

2001-2006 Cadillac Escalade Models

2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer Models

2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models

2001-2004 Oldsmobile Bravada

2005-2006 Saab 9-7X

 

with 4.8L or 5.3L VORTEC® GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z - RPOs LR4, LM7, LH6, L33, L59)

 

Supercede:

 

This bulletin is being revised to include engine RPO L59. Please discard Corporate Bulletin Number 06-06-01-019A (Section 06 - Engine/Propulsion System).

 

Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.

 

Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.

 

If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss.

 

<script language=JavaScript>

 

Refer to the illustrations on how to identify Castech casting and/or the very specific areas of the cylinder head(s) for a coolant leak from porosity.

 

Cylinder head(s) location of the Castech manufacturing casting logo (1).

 

<script language=JavaScript> <script language=JavaScript>

 

Close up view of the cylinder head(s) showing the Castech manufacturing casting logo (1).

 

<script language=JavaScript>

 

If the cylinder head(s) is a Castech casting (1), inspect the area around the five oil drain holes for witness marks indicating coolant seepage over time (2).

 

If No evidence of coolant loss is found on inspection of Castech casting cylinder head(s), follow normal diagnostic procedures in SI to determine the cause of the coolant loss.

 

<script language=JavaScript> <script language=JavaScript>

 

The crack location can be found in any of the five cylinder head(s) oil drains. This can be seen as a clean or shiny area, on an otherwise stained surface (1). Pressurizing the cooling system at this time may reveal coolant, air, or a combination, weeping in the described area. If inspection reveals evidence of coolant witness marks (1), replace the entire cylinder head(s) assembly.

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